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Object scala.util.hashing.MurmurHash3

object MurmurHash3 extends MurmurHash3

An implementation of Austin Appleby's MurmurHash 3 algorithm (MurmurHash3_x86_32). This object contains methods that hash values of various types as well as means to construct Hashing objects.

This algorithm is designed to generate well-distributed non-cryptographic hashes. It is designed to hash data in 32 bit chunks (ints).

The mix method needs to be called at each step to update the intermediate hash value. For the last chunk to incorporate into the hash mixLast may be used instead, which is slightly faster. Finally finalizeHash needs to be called to compute the final hash value.

This is based on the earlier MurmurHash3 code by Rex Kerr, but the MurmurHash3 algorithm was since changed by its creator Austin Appleby to remedy some weaknesses and improve performance. This represents the latest and supposedly final version of the algorithm (revision 136).

Source
MurmurHash3.scala
See also

https://github.com/aappleby/smhasher

Linear Supertypes

Type Members

class ArrayHashing[T] extends Hashing[Array[T]]

Value Members

final def !=(arg0: Any): Boolean

Test two objects for inequality.

returns

true if !(this == that), false otherwise.

Definition Classes
AnyRef → Any

final def ##(): Int

Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

returns

a hash value consistent with ==

Definition Classes
AnyRef → Any

final def ==(arg0: Any): Boolean

The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

returns

true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any

def arrayHash[T](a: Array[T]): Int

final def arrayHash[T](a: Array[T], seed: Int): Int

Compute the hash of an array.

Definition Classes
MurmurHash3

def arrayHashing[T]: ArrayHashing[T]

final val arraySeed: Int(1007110753)

final def asInstanceOf[T0]: T0

Cast the receiver object to be of type T0.

Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

returns

the receiver object.

Definition Classes
Any
Exceptions thrown

ClassCastException if the receiver object is not an instance of the erasure of type T0.

def bytesHash(data: Array[Byte]): Int

final def bytesHash(data: Array[Byte], seed: Int): Int

Compute the hash of a byte array. Faster than arrayHash, because it hashes 4 bytes at once.

Definition Classes
MurmurHash3

def bytesHashing: Hashing[Array[Byte]]

def clone(): AnyRef

Create a copy of the receiver object.

The default implementation of the clone method is platform dependent.

returns

a copy of the receiver object.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws( ... ) @native()
Note

not specified by SLS as a member of AnyRef

final def eq(arg0: AnyRef): Boolean

Tests whether the argument (that) is a reference to the receiver object (this).

The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false. null.eq(null) returns true.

When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

returns

true if the argument is a reference to the receiver object; false otherwise.

Definition Classes
AnyRef

def equals(arg0: Any): Boolean

The equality method for reference types. Default implementation delegates to eq.

See also equals in scala.Any.

returns

true if the receiver object is equivalent to the argument; false otherwise.

Definition Classes
AnyRef → Any

def finalize(): Unit

Called by the garbage collector on the receiver object when there are no more references to the object.

The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

Attributes
protected[lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
Note

not specified by SLS as a member of AnyRef

final def finalizeHash(hash: Int, length: Int): Int

Finalize a hash to incorporate the length and make sure all bits avalanche.

Definition Classes
MurmurHash3

final def getClass(): Class[_]

Returns the runtime class representation of the object.

returns

a class object corresponding to the runtime type of the receiver.

Definition Classes
AnyRef → Any
Annotations
@native()

def hashCode(): Int

The hashCode method for reference types. See hashCode in scala.Any.

returns

the hash code value for this object.

Definition Classes
AnyRef → Any
Annotations
@native()

final def isInstanceOf[T0]: Boolean

Test whether the dynamic type of the receiver object is T0.

Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

returns

true if the receiver object is an instance of erasure of type T0; false otherwise.

Definition Classes
Any

final def listHash(xs: collection.immutable.List[_], seed: Int): Int

Definition Classes
MurmurHash3

def mapHash(xs: Map[_, _]): Int

final val mapSeed: Int

final def mix(hash: Int, data: Int): Int

Mix in a block of data into an intermediate hash value.

Definition Classes
MurmurHash3

final def mixLast(hash: Int, data: Int): Int

May optionally be used as the last mixing step. Is a little bit faster than mix, as it does no further mixing of the resulting hash. For the last element this is not necessary as the hash is thoroughly mixed during finalization anyway.

Definition Classes
MurmurHash3

final def ne(arg0: AnyRef): Boolean

Equivalent to !(this eq that).

returns

true if the argument is not a reference to the receiver object; false otherwise.

Definition Classes
AnyRef

final def notify(): Unit

Wakes up a single thread that is waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
@native()
Note

not specified by SLS as a member of AnyRef

final def notifyAll(): Unit

Wakes up all threads that are waiting on the receiver object's monitor.

Definition Classes
AnyRef
Annotations
@native()
Note

not specified by SLS as a member of AnyRef

def orderedHash(xs: TraversableOnce[Any]): Int

final def orderedHash(xs: TraversableOnce[Any], seed: Int): Int

Compute a hash that depends on the order of its arguments.

Definition Classes
MurmurHash3

def orderedHashing: Hashing[TraversableOnce[Any]]

def productHash(x: Product): Int

final def productHash(x: Product, seed: Int): Int

Compute the hash of a product

Definition Classes
MurmurHash3

def productHashing: Hashing[Product]

final val productSeed: Int(-889275714)

def seqHash(xs: collection.Seq[_]): Int

final val seqSeed: Int

def setHash(xs: Set[_]): Int

final val setSeed: Int

def stringHash(x: String): Int

final def stringHash(str: String, seed: Int): Int

Compute the hash of a string

Definition Classes
MurmurHash3

def stringHashing: Hashing[String]

final val stringSeed: Int(-137723950)

final val symmetricSeed: Int(-1248659538)

final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef

def toString(): String

Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.

returns

a String representation of the object.

Definition Classes
AnyRef → Any

final val traversableSeed: Int(-415593707)

def unorderedHash(xs: TraversableOnce[Any]): Int

final def unorderedHash(xs: TraversableOnce[Any], seed: Int): Int

Compute a hash that is symmetric in its arguments - that is a hash where the order of appearance of elements does not matter. This is useful for hashing sets, for example.

Definition Classes
MurmurHash3

def unorderedHashing: Hashing[TraversableOnce[Any]]

final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... ) @native()

© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.12.9/scala/util/hashing/MurmurHash3$.html